Hi, I'd like to replace my Honeywell ST9400C programmer and Honeywell T40 thermostat with a new Nest.
It should be relatively straight forward, but the wiring diagrams of each aren't obvious and the programmer seems to have a lot of wires.... any ideas?
1 - there is a power switch to provide/cease power to the bolier and programmer 2 - the second set goes to the bolier to provide power there 3 - the 3rd set goes to the old thermostat
So the 3rd set move over to T1/T2 on the heatlink
Terminals 1/2 on the programmer have no connection. T3 is Hot Water on ad T4 is Heating on, so these go to 6/3 on the heatlink.
So that just leaves me with the 'Common' connection on the heatlink (5/2 on the heatlink)??????
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by reddwarfcrew » Sun Oct 01, 2017 11:51 am 
by Adam13 » Mon Jan 20, 2020 10:00 pm
